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Aug. 31, 2011 -- A daily dose of purple potatoes served plain may help your heart. That is, if you steer clear of the deep fryer and fatty toppings.

A new study shows that people who ate plain purple potatoes cooked in the microwave twice a day for a month lowered their blood pressure by 3%-4% without gaining weight.

Researchers say the blood pressure-lowering effects are likely due to the high concentration of antioxidants found naturally in potatoes. Antioxidants protect your body from molecules called “free radicals” that can damage healthy cells.

But the frying process destroys the healthy substances in potatoes.

"Mention 'potato' and people think 'fattening, high carbs, empty calories.' In reality, when prepared without frying and served without butter, margarine, or sour cream, one potato has only 110 calories and dozens of healthful phytochemicals and vitamins,” researcher Joe Vinson, PhD, of the University of Scranton, in Pennsylvania, says in a news release. “We hope our research helps to remake the potato's popular nutritional image."

Researchers say potatoes contain a variety of potentially beneficial phytochemicals at similar levels as broccoli, spinach, and Brussels sprouts.

Potatoes’ Surprising Effect

In the study, 18 overweight and obese people with high blood pressure either ate six to eight small purple potatoes (about the size of a golf ball) with the skins twice daily or no potatoes, as a part of their normal diet for four weeks.

The results showed that people who ate purple potatoes lowered their diastolic (the bottom number in a blood pressure reading) blood pressure by an average of 4.3% and systolic (the top number) by 3.5%.

Researchers say that blood pressure-lowering effect is nearly the same as with oatmeal.

Although the study used purple potatoes, which can increasingly be found in farmers markets, researchers say red and white potatoes may have similar effects.

They say the results are especially noteworthy because 14 of the 18 people in the study were already taking drugs to control their high blood pressure, yet still experienced a further lowering of their blood pressure. No other changes in body weight or cholesterol were found as a result of adding potatoes to the peoples’ diet.

Researchers say the potato is the most eaten vegetable in the U.S., but it’s gotten a bad rap.

"The potato, more than perhaps any other vegetable, has an undeserved bad reputation that has led many health-conscious people to ban them from their diet," Vinson says.

The results of the study were presented this week at the national meeting of the American Chemical Society in Denver.